Fry the peanuts in 2 tsp. roasted peanut oil until they’re golden. Chop with the pepper flakes and a few pinches salt and set aside. Slice off the bok choy stems and cut them into 1” pieces. Leave the leaves whole. When hot, add the garlic and ginger and stir-fry for 1 minute. Add the bok choy and a few pinches salt and stir-fry until wilted and glossy. Add the soy sauce and cornstarch and stir-fry for 1 or 2 minutes more or until the leaves are shiny and glazed. Add the crushed peanuts, toss, and serve.